Depending on what node positions are known, and whether or not the nodes are synchronized, several scenarios can arise. In the general trilateration problem [1]}, one computes the receiver position from measured distances from transmitters at known positions. For GPS positioning, a variant of trilateration where the receiver is also unsynchronized is used [2]}.
For the network self-calibration scenario, where both receivers and transmitters are at unknown positions, several formulations have been proposed, depending on the degree of synchronization. In the Time Of Arrival (TOA) formulation, all nodes are assumed to be synchronized and their positions are computed from measured pseudoranges [3]}, [4]}. In Time Difference Of Arrival (TDOA) [5]}, the transmitters are assumed to be unsynchronized and in Unsynchronized TDOA (UTDOA) all nodes are unsynchronized [6]}.
